Bag having cursor-actuated complementary closure strips

ABSTRACT

The present invention provides a bag comprising two generally parallel sheets ( 16, 18 ) forming the main walls of the bag, complementary closure strips ( 20, 22 ) fixed to respective ones of the sheets, and a cursor ( 50 ) for actuating the strips ( 20, 22 ) for closing and opening purposes, the bag being characterized in that it further comprises, parallel to the closure strips ( 20, 22 ), between said sheets ( 16, 18 ), and level with the mouth ( 12 ) of the bag, additional means in relief ( 100 ) disposed on the insides of the closure strips ( 20, 22 ), designed to provide sealing by forming a barrier between the sheets ( 16, 18 ) in the closed position of the bag, said additional means in relief ( 100 ) being placed facing the flanks ( 52, 54 ) of the cursor ( 50 ) to be urged towards their sealing position by the cursor ( 50 ) when the cursor is moved towards the sealing position.

[0001] The present invention relates to the field of bags havingcomplementary closure strips that are actuated by a cursor both foropening and for closing.

[0002] Such bags are described, for example, in documents EP-A-0 051010, EP-A-0 102 301, and EP-A-0 479 661.

[0003] Those bags that are cursor-actuated both for opening and forclosing have already given good service.

[0004] The cursors make the bags easier to open and close. The presenceof a cursor is particularly appreciated by the elderly and the visuallyhandicapped.

[0005] Nevertheless, most known bags with cursors do not give fullsatisfaction. In particular, most such bags are not totally leakproofwhen the strips are in the closed position. This lack of sealing is dueto the fact that the strips remain separate ahead of the cursor.

[0006] Nevertheless, leakproofing is required in numerous applications,particularly, but not exclusively, for bags that are used for freezingfoodstuffs.

[0007] Attempts have been made to remedy that drawback by proposingclosure strips that present a local discontinuity in the vicinity of theend which receives the cursor when the bag is in the closed position,such that the cursor penetrates into the discontinuity and ensures thatthe strips are perfectly engaged in one another over their entire lengthwhen in the closed position.

[0008] Nevertheless, the means proposed in that context turn out to bevery complex. Even so, they do not always ensure that the bags areperfectly sealed. In addition, they suffer from the major drawback ofnot retaining the cursor reliably and consequently of running the riskof the cursor being swallowed by small children, for example.

[0009] The object of the present invention is to improve the performanceof known cursor-fitted bags.

[0010] The main object of the present invention is to propose bagspresenting leakproofing that is better than that of previously knownbags.

[0011] Another object of the present invention is to propose means thatreduce the risk of the cursor being removed by mistake, specifically inorder to reduce the risk of the cursor being swallowed by youngchildren.

[0012] Another object of the present invention is to propose meansenabling bags to be produced automatically and at a high rate ofthroughput.

[0013] In the context of the present invention, these objects areachieved by a bag comprising two generally parallel sheets forming themain walls of the bag, complementary closure strips fixed to respectiveones of the sheets, and a cursor for actuating the strips for closingand opening purposes, the bag being characterized in that it furthercomprises, parallel to the closure strips, between said sheets, andlevel with the mouth of the bag, additional means in relief disposed onthe insides of the closure strips, designed to provide sealing byforming a barrier between the sheets in the closed position of the bag,said additional means in relief being adapted to be urged towards theirsealing position by the cursor when the cursor is moved towards itsposition for closing the bag.

[0014] In certain embodiments, said additional means in relief areplaced facing the flanks of the cursor.

[0015] As specified in greater detail below, such additional means inrelief can be formed, for example, by means of at least one bead securedto the inside surface of a sheet of the bag, or by means of twosymmetrical beads secured to the respective inside surfaces of the twosheets of the bag, or indeed by means of complementary male/femaleelements secured to respective inside surfaces of the two sheets of thebag.

[0016] According to another advantageous characteristic of the presentinvention, the bag, in the vicinity of its mouth includes means situatedon the side of the closure strips opposite from the side on which saidadditional leakproofing means are situated, and adapted to define thrustbetween opposing inside faces of the walls of the bag, and means areprovided on the cursor to urge the walls of the bag inwards in a zone ofsaid walls lying between the additional leakproofing means and thethrust means. This guarantees that said additional means are urged intoa sealing position by the cursor. This urging is preferably performed inregister with the closure strips.

[0017] The present invention also provides films fitted with suchsealing means and such closure strips, and also extruded tapes carryingsuch means.

[0018] According to another advantageous characteristic of the presentinvention, the bag comprises two generally parallel sheets forming themain walls of the bag, complementary closure strips fixed to respectiveones of said sheets in the vicinity of the mouth of the bag, and acursor having two side flanges interconnected by a web, the flangesbeing placed on the outsides of the sheets at the mouth of the bag andco-operating with a central elongate tongue to define two convergingpassages for the complementary closure strips, and the bag ischaracterized by the fact that the tongue is interrupted so as to be setback from the longitudinal end of the cursor, at least at the wider endof the cursor corresponding to the diverging ends of the passages, andthat the side flanges are provided in the vicinity of their free edgesremote from the web with urging means for urging the sheets of the bagtowards each other, said means occupying the entire longitudinal extentof the tongue and extending longitudinally beyond each end thereof so asto ensure that the bag is leakproof when it is in its closed position.

[0019] Other characteristics, objects, and advantages of the presentinvention will appear on reading the following detailed description withreference to the accompanying drawings, given by way of non-limitingexample, and in which:

[0020]FIG. 1 is a diagrammatic section view of a bag constituting afirst embodiment of the present invention;

[0021] FIGS. 2 to 11 are similar section views showing a first series ofvariant embodiments in accordance with the present invention;

[0022] FIGS. 12 to 29 show a second series of variant embodiments of thepresent invention;

[0023] FIGS. 30 to 39 show a third series of variant embodiments of thepresent invention;

[0024] FIGS. 40 to 42 are three diagrammatic cross-section views of abag fitted with a cursor of the present invention, on views givenreferences I-I, II-II, and III-III respectively in FIG. 43;

[0025]FIG. 43 is a longitudinal mid-section view of a cursor of thepresent invention, on a section plane referenced IV-IV in FIGS. 40 to42; and

[0026]FIG. 44 is another longitudinal section view of the cursor on asection plane referenced V-V in FIG. 43.

[0027]FIG. 1 shows a bag 10 whose mouth is referenced 12 and whosebottom is referenced 14.

[0028] The bag 10 is made up of two main sheets 16 & 18. These areinterconnected at their bottom 14 (by a fold, when the two sheets 16 &18 are originally a single sheet as shown in FIGS. 1 to 3, or by heatsealing or adhesive when the two sheets 16 & 18 are initially separatesheets that are superposed during manufacture, as shown in FIGS. 4 to 9,or indeed by heat sealing or adhesive along the edges of a single sheetthat is folded over at the mouth, e.g. as shown in FIGS. 10 and 11), andalso along two side edges perpendicular to the bottom 14 and the mouth12 (the side edges are preferably bonded together by heat sealing oradhesive).

[0029] At the mouth 12, the two sheets 16 & 18 are provided withcomplementary closure strips 20 & 22.

[0030] These complementary closure strips 20 & 22 can be implemented innumerous ways. The invention is not limited to the specific embodimentsshown in the accompanying figures. It should also be observed that twovariant embodiments of such closure strips 20 & 22 are shown in theaccompanying figures, respectively in one embodiment in FIGS. 1 to 3 and12 et seq, and another embodiment in FIGS. 4 to 11.

[0031] In particular, the invention applies to closure strips 20 & 22that are respectively of the male and female types as is well known tothe person skilled in the art and as is shown diagrammatically in FIGS.1 to 3 and 12 et seq. However the invention is not limited to thatparticular disposition and can also extend, for example, to closurestrips 20 & 22 of the hook type as shown in FIGS. 4 to 11.

[0032] As shown in FIGS. 1, 3 to 7, and 10, in particular, thecomplementary closure strips 20 & 22 can be extruded on the sheets 16 &18 constituting the bag (more precisely on the inside surfaces of saidsheets 16 & 18 in the embodiments of FIGS. 1 and 3 to 7, and on theoutside surfaces of said sheets in the embodiment of FIG. 10 where thesheets 16 & 18 form an inwardly-folded bellows at the mouth of the bagso as to form a tamperproofing web for indicating whether or not the baghas already been opened).

[0033] Nevertheless, in a variant embodiment, the closure strips 20 & 22can initially be formed on respective support webs 21 & 23 that arefitted to the sheets 16 & 18 level with the mouth 12 of the bag, asshown in FIGS. 2, 8, 9, and 11. In this case also, it will be observedthat in FIGS. 2, 8, and 9, the support webs 21 & 23 are fixed to theinside surfaces of the sheets 16 & 18. In contrast, in FIG. 11 thesheets 16 & 18 form a bellows that is folded into the bag at its mouthso as to form a tamperproofing web, with the support webs 21 & 23 beingfixed on the outside surfaces of the sheets 16 & 18.

[0034] The webs 21 & 23 can be bonded to the films 16 & 18 by anysuitable conventional means, e.g. by heat sealing or by adhesive.

[0035] The use of closure strips that are not extruded on the films 16 &18 but that are fitted thereto by heat sealing or adhesive is shown inthe accompanying drawings only in FIGS. 2, 8, 9, and 11. Nevertheless,the use of such closure strips 20 & 22 fitted to the films 16 & 18 canapply to all of the various embodiments of the invention.

[0036] As mentioned above in the context of the present invention, thebag also has a cursor 50 adapted to actuate the strips 20 and 22 foropening and closing purposes, and also, parallel to the closure strips20 and 22, between said sheets 16 and 18, and level with the mouth 12 ofthe bag, additional means in relief 100 designed to provide leakproofingby forming a barrier between the sheets 16 and 18 when the bag is in theclosed position, said additional means in relief 100 being placed inregister with the flanks 52 and 54 of the cursor 50 so as to be urgedtowards their sealing position by the cursor 50 when it is moved towardsits sealing position.

[0037] The cursor 50 can be embodied in numerous conventional ways. Inparticular, the cursor 50 can be in accordance with the dispositionsdescribed in document EP-A-0 479 661.

[0038] That is why the cursor 50 is not described in greater detailbelow.

[0039] Nevertheless, it should be observed that the cursor 50 which ismade of plastics material preferably has two side flanges 52 & 54 (or“flanks”) interconnected via a web 56 and co-operating with an elongatecentral tongue (not shown in the accompanying figures at the location ofthe section plane shown) to define two converging passages for theinterfittable complementary closure strips 20 & 22. Thus, when thedirection of relative displacement between the cursor 50 and the closurestrips 20 & 22 tends to move the cursor 50 so as to force the closurestrips 20 and 22 into engagement, the bag is closed. When the cursor 50is moved in the opposite direction, the bag is opened.

[0040] The films 16 & 18, the closure strips 20 & 22, and the additionalleakproofing means 100 can be made of any suitable plastics materialknown to the person skilled in the art. Preferably, they are made ofpolyolefin, most advantageously of low or high density polyethylene, oreven of polypropylene.

[0041] In the context of the present invention, it is preferable for themeans 100 to be placed on the inside of the closure strips 20 & 22 (i.e.towards the inside of the bag relative to the closure strips 20 & 22)and they preferably extend over the entire length of the bag (i.e. theyhave the same length as the closure strips 20 & 22).

[0042] In the first embodiment shown in FIG. 1, said additionalleakproofing means 100 are formed by a bead 102 parallel to the strip 20and secured to one of the sheets 16. In FIG. 1, this bead 102 isextruded on the film 16. However, in a variant, as mentioned above, thebead 102 could be extruded on a support web which is in turn secured tothe film 16.

[0043] Such a bead 102 is placed facing the flanks 52 & 54 of the cursor50 and on the inside thereof. Thus, the bead 102 is urged to pressagainst the opposite film 18 when the cursor 50 is moved to its closureposition.

[0044] The shape of the strips 20 & 22, of the means 100, and of thecursor 50 are preferably such that the flanks 52 & 54 of the cursor 50impose transverse play (i.e. perpendicularly to the sheets 16 & 18) onthe means 100 that is smaller than that tolerated for the closure strips20 & 22.

[0045] For this purpose, for example, when the inside surfaces of theflanks are parallel, as shown in the accompanying figures, the thicknessL₁ of the means 100 is greater than the thickness L₂ defined by theclosure strips 20 & 22 when they are mutually engaged.

[0046] This preferred relationship L₁>L₂ is not limited to theembodiment shown in FIG. 1 but applies to all embodiments of the presentinvention, including when said leakproofing means 100 are formed by twobeads or indeed by complementary male/female means, or by any otherequivalent means, as described below.

[0047] This disposition makes it possible to guarantee that the means100 provide a leakproof barrier between the two films 16 & 18.

[0048] In the embodiment shown in FIG. 2, the leakproofing means 100 areformed by two beads 104 & 106 respectively secured to each of the twofilms 16 & 18 and placed facing each other so as to have their topscoming into contact to form a leakproof barrier, when they have beenurged together by the flanks 52 & 54 of the cursor 50. In FIG. 2, thetwo beads 104 & 106 are symmetrical. However, in a variant, it ispossible to provide beads 104 & 106 that are asymmetrical.

[0049] In the embodiment shown in FIG. 3, the sealing means 100 areconstituted by complementary male/female elements 110 & 112 that aresecured to the respective inside surfaces of the two sheets 16 & 18 ofthe bag. Still more precisely, in FIG. 3, the female element 112 has twolips 1120 & 1122 adapted to rest against respective flanks of the maleelement 110. In FIG. 3, the two lips 1120 & 1122 are symmetrical.However, in a variant, it is possible to have two lips 1120 & 1122 thatare asymmetrical. The male element 110 is generally rounded in shape.

[0050] The leakproofing means 100 shown in FIG. 4 are identical to thoseof FIG. 3. However, in FIG. 4 it will be observed that the cursor 50 hasprojections 520 & 540 on the inside surfaces of its flanks 52 & 54,which projections are in register with the means 100 so as to ensurethat these means are urged into their leakproofing position when the bagis closed. Such projections 520 & 540 can be in a wide variety ofshapes. In a variant, such projections can be provided on the outsidesurfaces of the walls 16 & 18 where they face the cursor, or indeed suchprojections can be formed on the walls of the bag and other projectionsfacing them can be formed on the cursor 50.

[0051]FIG. 5 shows another variant embodiment in which the male element110 is substantially triangular in section. This structure guaranteesthat contact between the flanks of the male element 110 and the lips1120 & 1122 is reinforced when the male and female elements 110 & 112are urged together by the cursor 50.

[0052] In FIG. 5, it will also be observed that the two lips 1120 & 1122of the female element 112 are asymmetrical. The lip 1120 situated on theinside of the bag relative to the male element 110 is preferably longerand more flexible than the other lip 1122 that is situated towards theoutside of the bag. Thus, the pressure inside the bag, or indeed thecontents thereof acting directly, e.g. a liquid contents, presses thefirst lip 1120 elastically against the male element 110. In contrast,the second lip 1122 withstands such a force and therefore does not moveaway from the male element 110.

[0053] As shown in FIGS. 1 to 6 and 10, the means 100 can be extrudedonto the sheets 16 & 18 that constitute the bag (more precisely onto theinside surfaces of the sheets 16 & 18 in the embodiments of FIGS. 1 to6, and on the outside surfaces of the sheets in the embodiment of FIG.10 where the sheets 16 & 18 form an inwardly-folded bellows at the mouthof the bag so as to form a tamperproofing web).

[0054] Nevertheless, in a variant embodiment, the means 100 caninitially be formed on respective support webs 121 & 123 which areapplied to the sheets 16 & 18 in the vicinity of the mouth 12 of thebag, as shown in FIGS. 7 to 9 and 11. Here again it should be observedthat in FIGS. 7 to 9 the support webs 121 & 123 are fixed to the insidesurfaces of the sheets 16 & 18, whereas in FIG. 11 the sheets 16 & 18form a bellows that is folded into the bag at its mouth so as to form atamperproofing web, with the support webs 121 & 123 being fixed on theoutside surfaces of the sheets 16 & 18.

[0055] It would also be observed, as shown in FIGS. 8, 9 and 11, thesupport webs 121 & 123 can coincide respectively with the support webs21 & 23 of the closure strips 20 & 22.

[0056] The bonding between the webs 121 & 123 and the films 16 & 18 canbe provided by any suitable conventional means, e.g. heat sealing oradhesive.

[0057] The use of means 100 that are not extruded onto the films 16 &18, but that are fitted thereto by heat sealing or adhesive is shown inthe accompanying drawings only in FIGS. 7 to 9 and 11. However, the useof such means 100 fitted to the films 16 & 18 could apply to all of thevariant embodiments of the invention.

[0058] Accompanying FIG. 6 shows a variant embodiment in which grooves160 & 180 are provided that are open in the outside surfaces of the bag,respectively in register with the means 100, and specificallyrespectively in register with the female element 112 and with the maleelement 110, and also provides ribs 522 & 542 projecting from the insidesurfaces of the flanks 52 & 54 of the cursor 50, which ribs 522 & 542are adapted to penetrate into said grooves 160 & 180, respectively.

[0059] The operation defined in this way between the grooves 160 & 180and the ribs 522 & 542 can serve to improve the urging applied by thecursor 50 the means 100. This co-operation makes it possible to ensurethat the urging from the cursor 50 is applied in a precise zone. It alsomakes it possible to retain the cursor 50 quite safely on the bag. Thisco-operation prevents any unexpected removal of the cursor 50.

[0060] The use of ribs 522 & 542 with complementary grooves 160 & 180 isshown in the accompanying drawings only in FIG. 6. Nevertheless, the useof such ribs 522 & 542 and complementary grooves 160 & 180 can beapplied to all of the variant embodiments of the invention.

[0061] The embodiment of FIG. 7 is described above. It differsessentially from the embodiments shown in the earlier figures by thefact that the means 100 are carried by respective support webs 121 & 123fitted to the sheets 16 & 18, as mentioned above.

[0062] The embodiment of FIG. 8 is described above. It differsessentially from the embodiments shown in the previous figures by thefact that the means 100 are carried by respective support webs 121 & 123that also act as support webs 21 & 23 for the strips 21 and 22 and thatare fitted to the sheets 16 & 18, as mentioned above.

[0063] The same applies to the embodiment shown in FIG. 9. However inFIG. 9, the support webs 121 & 21 and 123 & 23 are interconnected by aloop 24. This loop is located on the inside of the means 100 and itsconcave side faces towards the outside of the bag.

[0064] Thus, these support webs 121, 21, 123, 23, and 24 form atamperproofing web for showing whether or not the mouth 12 has beenopened. In order to gain access to the inside of the bag it is necessaryto break the web 24. This tamperproofing web 24 constitutes a bellowsfolded towards the inside of the bag at its mouth 12 and it extends incontinuity from the support webs 121 & 21 and 123 & 23.

[0065]FIGS. 10 and 11 show variant embodiments in which such atamperproofing web, referenced 19, is formed by a fold in the filmconstituting the main sheets 16 & 18 of the bag. In FIG. 10, the strips20 & 22 and the means 100 are integrally molded on the film. Incontrast, in FIG. 11, the strips 20 & 22 and the means 100 are carriedby support webs 121 & 21 and 123 & 23 that are fitted to the film.

[0066] Such a bellows 19 directed towards the inside of the bag can beshaped by any suitable known means, e.g. by means of a blade urging thebellows 19 towards the inside between the sheets 16 & 18, as is wellknown to the person skilled in the art.

[0067] The person skilled in the art will readily understand that it isappropriate in entirely conventional manner to break the tamperprootingweb 24 or 19 in order to gain access to the substance contained insidethe bag 10.

[0068] Thus, the state of the web 24 or 19 serves to indicate whether ornot the bag 10 has already been used.

[0069] In order to make it easier to open the web 24 or 19, it can beprovided in conventional manner with a line of weakness or of scoring,e.g. halfway across its width, as shown diagrammatically under reference190 in FIGS. 10 and 11.

[0070] The bags obtained in application of the present invention providenumerous advantages over known prior bags.

[0071] In particular, they make it possible to have a high rate ofproductivity and to provide bags that are indeed leakproof.

[0072] Furthermore, the co-operation defined between the grooves 160 &180 and the ribs 522 & 542 of the cursors 50 makes it possible to avoidany unexpected removal of the cursors 50 under the effect of pressureinside the bags or under the effect of a user pulling too hard.

[0073] Where appropriate, in the embodiments shown in FIGS. 10 and 11where a tamperproofing web 19 is provided that is formed by a fold ofthe films from which the bags are made, a line of heat sealing can beprovided between the inside surfaces of the main sheets 16 & 18constituting the bag and segments 162 & 182 forming the bellows whichcorresponds to the tamperproofing web 19, as shown diagrammaticallyunder reference 60 in FIGS. 10 and 11.

[0074] Naturally, the present invention is not-limited to the particularembodiments described above, but extends to any variant coming withinthe spirit of the invention.

[0075] Bags of the present invention can be made on any suitable knowntype of machine, and in particular on form, fill, and seal (FFS) typemachines, i.e. machines that are designed to perform automatically theoperations of forming, filling, and sealing the bags.

[0076] The present invention also applies equally well toimplementations in which the closure strips are placed longitudinallyrelative to the travel direction of the film and to implementations inwhich the closure strips are disposed transversely.

[0077] In addition, the present invention applies equally well toimplementations in which the closure strips are prefitted with a cursoron being conveyed to the bag-forming machine, and to implementations inwhich the cursor is fitted to the strips subsequently.

[0078] It will also be observed that the present invention is notlimited to the grooves 160 & 180 and the ribs 522 & 542 having theshapes shown in accompanying FIG. 6. These grooves 160 & 180 and ribs522 & 542 can be implemented in a wide variety of right sections. Thus,for example, it is possible to envisage giving the grooves 160 & 180 aright section in which the sides converge, e.g. as a dovetail or in theform of a rail (e.g. a T-shaped rail). Such a disposition serves toreinforce retention of the cursor 50 on a bag.

[0079] As mentioned above, in the context of the present invention, itis preferable for the leakproofing means 100 and the closure strips 20 &22 to extend across the entire width of the bag. However, by definition,the cursor 50 occupies only a limited fraction of this width.Consequently, the cursor 50 cannot on its own urge against theleakproofing means 100 continuously over the entire length thereof.

[0080] As mentioned above, to ensure leakproofing, it is possible toconsider giving the means 100 a thickness L₁ that is greater than thethickness L₂ of the closure strips 20 & 22.

[0081] Other means can be provided to apply transverse pressure P at thewalls 16 & 18 on the means 100 when the bag is in its closed position inorder to ensure good leakproofing. This pressure P is showndiagrammatically in FIGS. 2 and 5. Nevertheless, in this case also thesedispositions can be applied to all embodiments of the present invention.

[0082] Thus, in the context of the present invention, in a variantthereof, the closure strips 20 & 22 are adapted to provide such pressureP automatically on the means 100 when the bag is closed.

[0083] Various shapes can be used for the closure strips 20 & 22 toachieve that.

[0084] When complementary closure strips of the male/female type areused as shown in FIG. 2, it is possible, for example, to provide anasymmetrical female strip, and in particular a strip in which L₃ is lessthan L₄, i.e. the size L₃ of the element 220 defining the inside lip ofthe female strip 22 is less than the corresponding size L₄ of theelement 222 defining the outside lip of the female strip 22.

[0085] The person skilled in the art will understand that by means ofthis disposition, the inner element 220 of the female strip 22 appliesstress to the leakproofing means 100 when the bag is in the closedstate, i.e. when the male element 20 is engaged in the female element22, and that this takes place along the entire length of the means 100.

[0086] A similar effect can be obtained with a male strip 20 that isasymmetrical (possibly in combination with a female strip 22 that islikewise asymmetrical as described above).

[0087] With complementary closure strips of the hook type as shown inFIG. 5, it is possible, for example, to provide for the twocomplementary hooks C1 & C2 situated towards the inside of the bag todefine, in the assembled position, a width L₅ between the inside facesof the sheets 16 & 18 that is less than the width L₆ taken between thesame faces of the sheets 16 & 18 level with the additional pair of hooksC3 & C4 situated towards the outside of the bag. This disposition makesit possible to provide the same stress over the full length of the means100.

[0088] As shown in FIG. 12, in a variant embodiment the two elements 104& 106 secured respectively to the inside surfaces of sheets 16 & 18 arenot positioned so as to come into contact via their tips, as describedabove with reference to FIG. 2, but are positioned so as to bejuxtaposed and so as to bear against each other via their adjacentfacing flanks 103 & 105 that extend generally perpendicularly to thesheets 16 & 18.

[0089] It will be observed that in the embodiments shown in FIGS. 12 etseq, the cursor 50 is preferably provided on the ends of its sideflanges 52 & 54 with respective rims 53 & 55 directed towards the insideof the bag. These rims 53 & 55 are positioned so as to be situatedbeyond the leakproofing means 100. The rims 53 & 55 contribute toleakproofing the bag. The rims 53 & 55 also participate in holding thecursor 50 on a bag so as to prevent unexpected removal of the cursor. Ascan be seen in FIG. 12, these rims 53 & 55 urge the sheets 16 & 18towards each other, beyond the leakproofing means 100.

[0090] It will also be observed that in the embodiments shown in FIGS.12 et seq, the portions of the support films 16 & 18 that are situatedin register with the closure strips 20 & 22 and the sealing means 100are preferably of thickness greater than the thickness of the remainderof the film constituting the bag. This greater thickness for the supportfilms 16 & 18 in register with the cursor 50 makes it possible to holdthe means 100 in their leakproofing position when the bag is in itsclosed position. Such localized extra thickness for the films 16 & 18can be obtained in the form of extra thickness formed during extrusionof the film, or it can be the result of fixing support webs for theclosure strips 20 & 22 or the means 100, as described above.

[0091]FIG. 13 shows another variant embodiment in which the two elements104 & 106 secured to the inside surfaces of the sheets 16 & 18respectively are provided at their tips with respective flanges 1040 &1060 that are orthogonal to said elements. Thus said flanges 1040 & 1060extend generally parallel to the sheets 16 & 18. The tips of theelements 104 & 106 bear against each other via the flanges 1040 & 1060.

[0092] In the embodiment of FIG. 13, said flanges 1040 & 1060 extendtowards the inside of the bag. In a variant, provision can be made forthe flanges 1040 & 1060 to be directed on the contrary towards theoutside of the bag. In yet another variant, provision can be made forsuch flanges 1040 & 1060 on the tips of the elements 104 & 106 to extendboth towards the inside and towards the outside of the bag. Under suchcircumstances, the elements 104 & 106 together with their flanges 1040 &1060 are generally T-shaped.

[0093]FIG. 14 shows a variant of the FIG. 12 embodiment in which atleast one of the two juxtaposed elements 104 & 106 is provided at itstip with an orthogonal flange 1060. This flange is designed to restagainst the inside face of the sheet 16 opposite so as to improveleakproofing. In FIG. 14, such a flange 1060 is shown on only one of theelements 106. Nevertheless, in a variant, provision can be made for suchan additional flange to be provided on the tips of both elements 104 &106 for the purpose of pressing against the inside faces of the oppositesheets.

[0094]FIG. 15 shows another variant of FIG. 12 in which the twojuxtaposed elements 104 & 106 are provided at their tips with roundedbulges 1042 & 1062. Each bulge is designed to rest against the insideface of the opposite sheet 16 & 18 in order to improve leakproofing. InFIG. 15, one such bulge is provided on each of the two elements 104 &106. In a variant, such a bulge 1042 & 1062 can be provided on only oneof the elements 104 & 106. In FIG. 15, these bulges are of circularright section and they are symmetrical about the midplanes of theelements 104 & 106. Nevertheless, the invention is not limited to thatparticular shape.

[0095]FIG. 16 shows a variant of FIG. 13 in which the cursor 50 is alsoprovided at the ends of each of the rims 53 & 55 with additional flanges530 & 550 that are directed towards the web 56 of the cursor 50, i.e.towards the outside of the bag. These flanges 530 & 550 thus extendgenerally parallel to the side flanges 52 & 54 of the cursor 50. Theseadditional flanges 530 & 550 are designed to occupy positions in thevolume defined between the sheets 16 & 18 and the flanges 1040 & 1060 ofthe leakproofing means 100. On examining FIG. 16, it will be understoodthat these flanges 530 & 550 serve to crease the sheets 16 & 18, therebyfurther reinforcing the leakproofing of the resulting bags.

[0096] In the embodiments described above, the cursor 50 is symmetricalabout a longitudinal plane. Thus, in FIGS. 12 to 14, its flanks 52 & 54are provided with respective rims 53 & 55.

[0097] However, in the variant shown in FIG. 17, the cursor isasymmetrical in that only one of its flanks, its flank 52, is providedwith a rim 53 that extends towards the inside of the bag.

[0098]FIG. 18 shows a variant of the FIG. 17 embodiment in which saidrim 53 is provided on its inside face with a bead 532 directed towardsthe web 56 so as to urge the two juxtaposed elements 104 & 106 to bearagainst each other via their adjacent flanks 103 & 105. For thispurpose, the bead 532 exerts force an the element 104 that is directedtowards the web 56.

[0099]FIG. 19 shows another variant embodiment in which the portions ofthe support films 16 & 18 that carry the closure strips 20 & 22 and theleakproofing means 100 are not situated directly in line with the sheetsconstituting the body of the bag, but are offset towards the outside ofthe bag via respective setbacks 1600 & 1800. These setbacks 1600 & 1800can be obtained by extrusion while manufacturing the film, or they canbe obtained subsequently by folding the film. On examining FIG. 19, itwill be understood that such setbacks 1600 & 1800 can facilitatejuxtaposing the sheets 16 & 18 at the outlet from the cursor 50 eventhough the sheets 16 & 18 are necessarily separated from each otherinside the cursor because of the presence of the closure strips 20 & 22and of the means 100.

[0100] On examining FIG. 19, it will also be observed that, whereappropriate, one of the setbacks 1800 can itself be provided with anextension 1802 directed towards the opposite support sheet 16. Thisextension 1802 is designed to rest against the opposite setback 1600 soas to further reinforce the leakproofing of the resulting bags.

[0101]FIG. 20 shows a variant embodiment in which provision is madefirstly for a bead 530 or inwardly-directed rim on the cursor on itssingle rim 53, and secondly for an element 106 projecting from the sheet18. Thus, as can be seen in FIG. 20, the bead 530 imparts a curve orbaffle-path to the second sheet 16 on leaving the cursor 50 suitable forfurther improving leakproofing of the resulting bag.

[0102]FIG. 21 shows a variant of the FIG. 12 embodiment in which atleast one of the two elements 104 & 106 is of thickness that increasesgoing towards its tip, or possesses a sloping flank such that it exertsa force on the other juxtaposed elements 106 & 104 when the bag is inits closed position.

[0103]FIG. 22 et seq show variant embodiments in which the leakproofingmeans 100 are essentially formed by structures that are flexible andresilient, so as to be deformable while the bag is being closed, whereasin the embodiments shown in FIGS. 12 to 21, the means 100 areessentially rigid.

[0104] Thus, FIG. 22 shows a variant embodiment in which theleakproofing means 100 comprise a flexible and resilient curved lip 130secured to the sheet 18 that carries the female closure strip 22.

[0105] In a variant, such a flexible and resilient lip 130 can besecured to the sheet 16 which carries the male closure strip 20.

[0106] In FIG. 22, the lip 130 is constituted by a sector of a cylindersubtending an angle at the center of more than 180°. In FIG. 22, theconcave side of the lip 130 is directed towards the inside of the bag.Nevertheless, in a variant, it is possible to provide for the concaveside of the lip 130 to be directed towards the outside of the bag.

[0107] As can be seen in FIG. 22, when the bag is in its closedposition, the tip of the lip 130 rests against the opposite supportsheet 16. As can be seen in FIG. 23, when the bag is open, said lip 130extends beyond the associated closure strip 22. This dispositionguarantees that when the bag is in the closed state, said lip 130 exertspressure on the opposite sheet 16.

[0108]FIG. 24 shows a variant of the FIG. 22 embodiment in which theposition of the lip 130 and the shape of the lip 130 are such that whensaid lip 130 is resting against the opposite sheet 16 it receives areaction which urges it itself to press against one of the closurestrips, and specifically the female closure strip 22 in this case.

[0109]FIG. 25 shows another variant embodiment in which such urging ofthe lip 130 to bear against the female closure element 22 is reinforcedby the presence on the inside surfaces of the flanks 52 & 54 of thecursor 50 of beads 520 & 540. Specifically, as shown in FIG. 25, thesebeads 520 & 540 are generally triangular in profile. Nevertheless, thebeads 520 & 540 are not limited to that particular shape and can beembodied in a wide variety of ways.

[0110] It will be observed in FIG. 25 that the central tongue of thecursor 50 which controls both engagement and disengagement of theclosure strips 20 & 22 is referenced 57.

[0111]FIG. 26 is a side view of the bag when fitted in this way. In thisFIG. 26, there can be seen a cursor 50 that has such pressure-applyingbeads 520 & 540 and there can also be seen the closure strips 20 & 22and the leakproofing means 100. On examining FIG. 26, it will beobserved that the beads 520 & 540 preferably extend over a portion onlyof the length of the cursor 50 and that they converge towards the topweb 56 of the cursor 50 on moving closer to the end of the cursor 50that is situated adjacent to the opening of the bag. By means of thisdisposition, the beads 520 & 540 urge the lip 130 to press against theclosure strip 22 in the vicinity of the open zone of the bag.

[0112] Similarly, the rims 53 & 55 provided on the flanges 52 & 54 ofthe cursor 50 can converge towards the web 56 as they come closer to theend of the cursor 50 which is situated adjacent to the opening of thebag, for the purpose of improving bag leakproofing at this point.

[0113]FIG. 27 shows another variant embodiment in which each of the twosheets 16 & 18 is provided on its inside surface with a resilient lip130 in the form of a cylindrical sector. These two lips 130 thus havetheir tips bearing against each other when the bag is closed.

[0114] In this case also, to achieve this effect at least one of the twolips 130 when in the rest position, i.e. when the bag is open,preferably extends beyond the associated closure strip, as showndiagrammatically in FIG. 28.

[0115] The cursor 50 used in the variant embodiment of FIG. 27 can alsoinclude pressure-applying beads 520 & 540 that extend upwards, as shownin FIG. 26, so as to urge the resilient lips 130 against the closurestrips 20 & 22 when the bag is in its closed position.

[0116]FIG. 29 shows another variant embodiment in which each of the twosupport films 16 & 18 is provided with a resilient lip 130, but in thiscase the lips are not positioned so as to come into contact with eachother via their tips, but so as to be juxtaposed laterally, as can beseen in FIG. 29. For this purpose, the two lips 130, each formed by acylindrical sector having an angle at the center of more than 1800, havetheir respective concave sides directed one towards the inside and theother towards the outside of the bag.

[0117] The description below relates to the variant embodiment shown inaccompanying FIGS. 30 to 39.

[0118] As mentioned above, in these variants, the bag has means 150 atits mouth 12, said means 150 being situated on the opposite side of theclosure strips 20 & 22 to said additional leakproofing means 100 andbeing adapted to ensure pressure is applied between facing inside facesof the walls of the bag. In addition, the cursor 50 is provided withmeans suitable for urging the walls of the bag inwards in a zone of saidwalls that extends between the additional leakproofing means 100 and thethrust means 150. This guarantees that said additional means 100 areurged into a leakproofing position by the cursor 50. This urging ispreferably performed in register with the closure strips 20 & 22.

[0119] As can be seen in the accompanying figures, it is thus preferablefor the additional leakproofing means 100 to be situated on the insideof the closure strips 20 & 22 while the thrust-defining means 150 aresituated on the outside of said closure strips 20 & 22.

[0120] This disposition having means 150 associated with the meansenabling the cursor 50 to press together the leakproofing means 100 canbe applied to all of the variant embodiments described above. They aretherefore not limited to the embodiments of FIGS. 30 to 39. Inparticular, this disposition applies to any type of leakproofing means100, to any type of closure strip 20 & 22, and to all variants of thecursor 50, or to a bag fitted with a tamperproofing web, etc. . . . .

[0121]FIG. 30 shows a variant in which the additional leakproofing means100 are formed by two flexible resilient lips 170 & 172 that are securedto the respective inside faces of the walls 16 & 18, and that extendtowards the inside and towards the bottom of the bag. In a variant,these lips 170 & 172 can be directed towards the inside of the cursor 50(in particular with bags containing a vacuum, for example). As mentionedabove, the disposition having thrust means 150 applies to any type ofleakproofing means 100 and is not limited to the means 100 shown in FIG.30. In particular, it applies to lips 170 & 172 that are notsymmetrical.

[0122] Similarly, in FIG. 30, the closure strips 20 & 22 are of themale/female type. Nevertheless, the invention applies to any type ofclosure strip, and in particular to hook-type strips.

[0123] In FIG. 30, the thrust means 150 are constituted by twosymmetrical elements 152 & 154 secured to respective inside faces of thewalls 16 & 18 at the mouth of the bag. More precisely, and still withreference to FIG. 30, each of these elements 152 & 154 has a rectangularright section that extends towards the midplane of the bag where saidelements come to bear against each other, when the bag is in its closedposition. Thus, these elements 152 & 154 extend generallyperpendicularly to said midplane.

[0124] It will be observed that in FIG. 30, the means 100, the strips 20& 22, and the means 150 are integrally formed with the walls 16 & 18 ofthe same material(s), preferably by extrusion. More precisely, it willbe observed that the segments of the walls that extend between theleakproofing means 100 and the thrust means 150 are thicker than thesheets 16 & 18 constituting the remainder and the major portion of thebags. Thus, the above-mentioned segments are somewhat stiff between themeans 100 and the means 150.

[0125] The person skilled in the art will understood that by means ofthe above-mentioned characteristics, when the elements 152 & 154 arepressed against each other and the cursor 50 is pressing against theabove-mentioned segments of the walls 16 & 18 situated between the means100 and 150, the leakproofing means 100 are themselves urged into theirposition of contact and maximum leakproofing.

[0126] In FIG. 31, there can be seen the urging means provided on thecursor 50 in the form of beads 520 & 540 provided on the inside surfacesof the flanges 52 & 54 in register with the closure strips 20 & 22. Inthis case, the beads are in the form of cylindrical caps, but theinvention is not limited to that particular shape.

[0127] In FIG. 31, the force exerted by the cursor 50 on the mouthsegments of the bag walls is referenced F₁, the reaction due to themeans 150 is referenced F₂, and the force then exerted on theleakproofing means 100 is referenced F₃.

[0128] It will also be observed in FIG. 31 that the above-mentionedsegments define a cage in the vicinity of the mouth of the bag, whichcage has a right section that is rectangular and that projects from themain walls 16 & 18 of the bag. In other words, the main walls of the bagare not coplanar with the outside surfaces of the segments, but are setback inwards therefrom by a distance d. A setback is thus defined in thewalls 16 & 18 which serves as a bearing surface for the rims 53 & 55provided on the flanges 52 & 54 of the cursor 50 so as to prevent thecursor being removed unexpectedly.

[0129]FIG. 32 shows a variant in which such a setback is omitted. Thus,in FIG. 32, the main walls of the bag when at rest are, on the contrary,coplanar with the outside surfaces of the segments situated between themeans 100 and 150. Nevertheless this variant can also co-operate with acursor 50 having rims 53 & 55 on its flanges 52 & 54, because it ispossible to deform the sheets 16 & 18.

[0130] In the variant shown in FIG. 33, the above-mentioned segmentsbetween the means 100 and 150 do not define a cage of rectangular rightsection at the mouth of the bag, but define a cage that is generallyrounded.

[0131] In above-described FIGS. 30 to 33, the thrust elements 152 & 154are symmetrical and make contact with each other in the midplane of thebag. In a variant, these elements 152 & 154 can be asymmetrical, therebymaking contact with each other of the midplane. FIG. 34 thus shows avariant in which only the wall 18 is provided with a thrust element 154projecting from its inside face. This element 154 is adapted to restagainst the inside face of the opposite wall 16.

[0132] In above-described FIGS. 30 to 34, the leakproofing means 100,the closure strips 20 & 22, and the thrust means 150 are integrallyformed by extrusion out of the same material(s) as the walls 16 & 18. Ina variant, these various means can be supplied on respective supportwebs that are then secured to the inside faces of the sheets 16 & 18,e.g. by heat sealing or adhesive. These webs can be respective separatesupport webs for each of the means 100, strips 20 & 22, and means 150,or else support webs that are common to a plurality of these means.Thus, for example, FIG. 35 shows a variant embodiment in which the means100, the closure strips 20 & 22, and the thrust means 150 are carried bytwo respective webs, one of which is fixed to the inside face of thesheet 16 and the other of which is fixed to the inside face of the sheet18.

[0133]FIG. 36 shows a variant embodiment in which the urging means areformed not by beads secured to the inside faces of the flanges of thecursor, but by beads 15 projecting from the outside faces of the wallsegments situated between the means 100 and 150, preferably in registerwith the closure strips 20 & 22. In yet another variant, it is thuspossible to provide beads simultaneously on the cursor and on the wallsof the bag.

[0134]FIG. 37 shows another variant embodiment in which the facing endsof the thrust means forming the elements 152 & 154 are enlarged so as toguarantee that they bear against each other and so as to ensure thatthese elements are not shifted so as to be no longer adjacent, sinceunder such circumstances the lever arms required for exerting thrust onthe means 100 would not be obtained. In FIG. 37, the adjacent ends ofthe elements 152 & 154 are of generally triangular right section withthe base of each triangle being situated in the plane of contact.Nevertheless, the invention is not limited to this particulardisposition.

[0135]FIG. 38 shows a variant in which the cursor 50 is fitted on theinside faces of its flanges 52 & 54 with projecting structures 522 & 542of right section complementary to grooves 13 formed in theabove-mentioned beads 15, the structures 522 & 542 being engaged in saidgrooves 13. Still more precisely, the structures 522 & 542 flare whilethe grooves 13 have edges that converge. This disposition serves toprevent unwanted removal of the cursor 50.

[0136]FIG. 39 shows another variant embodiment in which complementaryshape means are defined between the cursor 50 and the walls of the bagin the vicinity of the rims 53 & 55 formed on the flanges 52 & 54, inthe form of elements 530 & 550 of the kind described above.

[0137] Where appropriate, the elements constituting the leakproofingmeans 100 can be coextruded with the bag and/or the closure strips, outof a material that is more flexible than the material forming the otherportions. For example, the lips 170 & 172 can be coextruded out of acopolymer of ethylene or using a synthetic elastomer.

[0138] As mentioned above, the present invention is naturally notlimited to the particular embodiments described above, but it extends toany variant within the spirit of the invention.

[0139] The term “leakproofing” is used in the context of the presentinvention to indicate that the means 100 are adapted (by their shapeand/or their thrust force) either to provide a complete barrierpreventing any penetration from the outside towards the inside of thebag or any leakage from the inside towards the outside of the bag, orelse to act as means that provide a barrier in one direction, i.e. toprevent penetration from the outside towards the inside of the bag, orto prevent leakage from the inside towards the outside of the bag.

[0140] It should also be observed that the rim means 53 & 55 and thestructures such as 522 & 542 provided on the bag and contributing toholding the cursor 50 on the bag are generally not the only structuresthat provide such holding, but for example provide assistance for thispurpose for flared means provided in the central tongue of the cursor50.

[0141] The person skilled in the art will also understand that in theembodiments shown in FIGS. 30 to 39, the leakproofing means 100 need notbe placed facing the flanks 52 & 54 of the cursor, but can be placedoutside them. In other words, under such circumstances, the end of thecursor is situated between said means 100 and the closure strips 20 &22.

[0142] As mentioned above, in a variant embodiment the tongue 59 isinterrupted before the longitudinal end of the cursor (i.e. the tongueis set back from the end), at least at the broader end of the cursorwhich corresponds to the diverging end of the passages 590 & 592, as canbe seen in particular in FIGS. 40, 42, 43, and 44, and the side flanges52 & 54 are provided in the vicinity of their free edges remote from theweb 56 with urging means 520 & 540 for urging the sheets 16 & 18 of thebag towards each other, which means cover the entire longitudinal extentof the tongue 59 and extend longitudinally beyond the ends of thetongue, so as to ensure that the bag is leakproof when in the closedposition.

[0143] In the preferred embodiment shown in FIGS. 40 to 43, these urgingmeans are constituted by ribs 520 & 540 projecting towards the inside ofthe cursor 50 from the edges of the flanges 52 & 54 remote from the web56, or where appropriate from part of the way along the height of theinside surfaces of the flanges 52 & 54 lying between the web 56 and thefree edges of the flanges 52 & 54. It will be observed that although theribs 520 & 540 are not necessarily situated at the free edges of theside flanges 52 & 54, these ribs 520 & 540 are nevertheless situatedbeyond the tongue 59 (i.e. between the tip of the tongue 59 remote fromthe web 56 and the free edges of the flanges 52 & 54), so that the ribsare not level with the tongue.

[0144] The ribs 520 & 540 overlie the tongue 59 without discontinuityand extend beyond it, at least at the broader end of the tongue 59corresponding to the diverging end of the passage 590 & 592. Moreprecisely, in the preferred embodiment shown in the accompanyingfigures, the ribs 520 & 540 extend over the full length of the cursor 50while the tongue 59 is interrupted at its broader end (diverging end ofthe passages 590 & 592) at a distance l₁ from the end of the cursor 50,while at its narrower end (converging end of the passages 590 & 592), itterminates at a distance l₂ from the end of the cursor 50.

[0145] The width l₆ of the empty space defined between the tips of theribs 520 & 540 is substantially equal to the sum of the thicknesses ofthe sheets 16 & 18 at the mouth of the bag. Thus, the cursor 50 urgesthe sheets towards each other beneath the tip of the tongue 59, therebyguaranteeing that the bag is leakproof.

[0146] In the embodiment shown in accompanying FIGS. 40 to 44, two ribs520 & 540 are provided that are symmetrical and of the same height, onerib on each of the flanges 52 & 54. In a variant, ribs 520 & 540 can beprovided that are asymmetrical. Thus, it is possible to provide a singlerib on only one of the flanges 52 & 54 of the cursor 50.

[0147] In the figures, the following are referenced:

[0148] l₃ the height of the tongue 59 measured parallel to the flanges52 & 54 and perpendicularly to the web 56;

[0149] l₄ the distance between the free tip of the tongue 59 remote fromthe web 59 and the ribs 520 & 540; and

[0150] l₅ the width of the tongue 59 at its broader end.

[0151] In the context of the present invention:

[0152] l₁ preferably lies in the range 1 mm to 10 mm, and is mostpreferably about 3 mm;

[0153] l₂ preferably lies in the range 0.5 mm to 10 mm, and is mostpreferably about 4 mm;

[0154] l₃ preferably lies in the range 2 mm to 7 mm, and is mostpreferably about 3 mm;

[0155] l₄ preferably lies in the range 5 mm to 15 mm, and is mostpreferably about 8 mm;

[0156] l₅ preferably lies in the range 0.3 mm to 2 mm, and is mostpreferably about 0.5 mm; and

[0157] l₆ preferably lies in the range 50 μm to 2.5 mm, and is mostpreferably about 200 μm.

[0158] In the context of the present invention:

[0159] the ratio l₁/l₅ preferably lies in the range 0.5 to 30, and ismost preferably about 6;

[0160] the ratio l₂/l₅ preferably lies in the range 2.5 to 30, and ismost preferably about 8;

[0161] the ratio l₁/l₃ preferably lies in the range 0.5 to 5, and ismost preferably about 1;

[0162] the ratio l₂/l₃ preferably lies in the range 0.1 to 5, and ismost preferably about 1.3;

[0163] the ratio l₁/l₄ preferably lies in the range 0.05 to 2, and ismost preferably about 0.4; and

[0164] the ratio l₂/l₄ preferably lies in the range 0.05 to 2, and ismost preferably about 0.5.

1/ A bag comprising two generally parallel sheets (16, 18) forming themain walls of the bag, complementary closure strips (20, 22) fixed torespective ones of the sheets, and a cursor (50) for actuating thestrips (20, 22) for closing and opening purposes, the bag beingcharacterized in that it further comprises, parallel to the closurestrips (20, 22), between said sheets (16, 18), and level with the mouth(12) of the bag, additional means in relief (100) disposed on theinsides of the closure strips (20, 22), designed to provide sealing byforming a barrier between the sheets (16, 18) in the closed position ofthe bag, said additional means in relief (100) being adapted to be urgedtowards their sealing position by the cursor (50) when the cursor ismoved towards its position for closing the bag. 2/ A bag according toclaim 1, characterized by the fact that the additional leakproofingmeans (100) are constituted by at least one bead (102; 104, 106) securedto the inside surface of a sheet (16) of the bag. 3/ A bag according toclaim 1 or 2, characterized by the fact that the additional leakproofingmeans (100) are made up of two beads (104, 106) secured respectively tothe inside surfaces of the two sheets (16, 18) of the bag. 4/ A bagaccording to claim 1, characterized by the fact that the additionalleakproofing means (100) are constituted by complementary male/femaleelements (110, 112) respectively secured to the inside surfaces of thetwo sheets (16, 18) of the bag. 5/ A bag according to claim 4,characterized by the fact that the male element (110) is substantiallytriangular in section. 6/ A bag according to claim 4 or 5, characterizedby the fact that the female element (112) has two lips (1120 and 1122)that are asymmetrical. 7/ A bag according to any one of claims 4 to 6,characterized by the fact that the lip (1120) of the female element(112) situated closer to the inside of the bag relative to the maleelement (110) is longer and more flexible than the second lip (1122)thereof situated towards the outside of the bag. 8/ A bag according toany one of claims 1 to 7, characterized by the fact that the additionalleakproofing means (100) extend over the entire length of the bag. 9/ Abag according to any one of claims 1 to 8, characterized by the factthat the shapes of the strips (20, 22), of the additional means (100),and of the cursor (50) are such that the flanks (52, 54) of the cursor(50) impart transverse play to the means (100) smaller than that whichis tolerated for the closure strips (20, 22). 10/ A bag according to anyone of claims 1 to 9, characterized by the fact that the inside surfacesof the flanks (52, 54) of the cursor (50) are parallel, and thethickness (L₁) of the leakproofing means (100) is greater than thethickness (L₂) defined by the closure strips (20, 22) when they aremutually engaged. 11/ A bag according to any one of claims 1 to 10,characterized by the fact that the cursor (50) has beads (520, 540) onthe inside surfaces of its flanks (52, 54), the beads being placed inregister with the leakproofing means (100) to guarantee that said meansare urged towards a leakproofing position when the bag is closed. 12/ Abag according to any one of claims 1 to 11, characterized by the factthat the walls of the bag have beads faced in register with theleakproofing means (100) and in register with the flanks of the cursor(50) to guarantee that the leakproofing means (100) are urged into aleakproofing position when the bag is closed. 13/ A bag according to anyone of claims 1 to 12, characterized by the fact that it comprises bothgrooves (160, 180) opening out to the outside surface of the bag,respectively in register with the leakproofing means (100), and alsoribs (522 and 542) projecting from the inside surfaces of the flanks (52and 54) of the cursor (50), which ribs (522 and 542) are adapted topenetrate respectively into said grooves (160 and 180). 14/ A bagaccording to any one of claims 1 to 13, characterized by the fact thatit includes means (19, 24) forming a tamperproofing web at the mouth(12) to show whether or not the bag has been opened. 15/ A bag accordingto claim 14, characterized by the fact that the tamperproofing web (24)forms a bellows that is folded towards the inside of the bag at themouth (12) and in continuity with the support webs (121, 21 and 123, 23)for the closure strips or the additional leakproofing means. 16/ A bagaccording to claim 14, characterized by the fact that the tamperproofingweb (19) is formed by a bellows folded towards the inside of the bag atthe mouth (12) in continuity with the film constituting the bag. 17/ Abag according to any one of claims 1 to 16, characterized by the factthat the bag (10) is made from a single film that is folded over ontoitself with the fold constituting the bottom (14) of the bag. 18/ A bagaccording to any one of claims 1 to 16, characterized by the fact thatthe bag (10) is formed from a single film that is folded over ontoitself with the fold being at the mouth (12) of the bag. 19/ A bagaccording to any one of claims 1 to 16, characterized by the fact thatthe bag (10) is made from two sheets (16, 18) that are initiallyseparate and that are superposed during manufacture. 20/ A bag accordingto any one of claims 1 to 19, characterized by the fact that thecomplementary closure strips (20, 22) and/or the additional leakproofingmeans (100) are extruded together with the sheets (16, 18) constitutingthe bag. 21/ A bag according to any one of claims 1 to 19, characterizedby the fact that the complementary closure strips (20, 22) and/or theadditional leakproofing means (100) are initially formed on respectivesupport webs(21, 23; 121, 123) that are fitted to the sheets (16, 18) atthe mouth (12) of the bag. 22/ A bag according to any one of claims 1 to19 and 21, characterized by the fact that the complementary closurestrips (20, 22) and the additional leakproofing means (100) areinitially formed on common support webs (21, 23; 121, 123) that aresecured to the sheets (16, 18) at the mouth (12) of the bag. 23/ A bagaccording to any one of claims 1 to 22, characterized by the fact thatthe closure strips (20, 22) are adapted to provide transverse urging (P)automatically on the leakproofing means (100) when the bag is closed.24/ A bag according to any one of claims 1 to 23, characterized by thefact that the complementary closure strips (20, 22) are of themale/female type and they comprise at least one asymmetrical male orfemale strip. 25/ A bag according to claim 24, characterized by the factthat the height occupied (L₃) by the element (220) defining the innerlip of the female strip (22) is less than the height occupied (L₄) bythe element (222) defining the outer lip of the female strip (22). 26/ Abag according to any one of claims 1 to 23, characterized by the factthat the complementary closure strips (20, 22) are of the hook type andpossess at least two pairs of complementary hooks defining widths in theassembled position that are different from one pair of hooks to theother. 27/ A bag according to claim 26, characterized by the fact thatthe two complementary hooks (C1, C2) situated towards the inside of thebag define, in the assembled position, a width (L₅) between the insidefaces of the sheets (16, 18) that is smaller than the width (L₆) takenbetween the same faces of the sheets (16, 18) in the vicinity of thepair of complementary hooks (C3, C4) situated towards the outside of thebag. 28/ A bag according to any one of claims 1 to 27, characterized bythe fact that the additional leakproofing means for providingleakproofing (100) are made up of two elements (104, 106) respectivelysecured to the inside surfaces of the two sheets (16, 18) of the bag anddesigned to bear against each other via their tips. 29/ A bag accordingto any one of claims 1 to 27, characterized by the fact that theadditional leakproofing means (100) are made up of two elements (104,106) secured respectively to the inside surfaces of the two sheets (16,18) of the bag and designed to be juxtaposed so as to bear against eachother via adjacent facing flanks (103, 105) that are generallyperpendicular to the sheets (16 and 18). 30/ A bag according to any oneof claims 1 to 27, characterized by the fact that the cursor (50) isprovided on the ends of at least one of its side flanges (52, 54) withrims (53, 55) directed towards the inside of the bag and positioned soas to be situated beyond the leakproofing means (100). 31/ A bagaccording to claim 30, characterized by the fact that the cursor (50) isalso provided at the end of said rim (53, 55) with an additional flange(530, 550) directed towards the web (56) of the cursor (50), i.e.towards the outside of the bag. 32/ A bag according to any one of claims1 to 31, characterized by the fact that the portions of the supportfilms (16, 18) situated facing the closure strips (20, 22) and theleakproofing means (100) are of thickness greater than the thickness ofthe remainder of the film constituting the bag. 33/ A bag according toclaim 32, characterized by the fact that the local extra thickness ofthe films (16, 18) is obtained in the form of extra thickness formedduring extrusion of the film. 34/ A bag according to claim 32,characterized by the fact that the local extra thickness of the films(16, 18) results from support webs for the closure strips (20, 22) orfor the leakproofing means (100) being fixed thereto. 35/ A bagaccording to claim 3 or 28, characterized by the fact that the twoelements (104, 106) secured respectively to the inside surfaces of thesheets (16, 18) are provided at their tips with at least one respectiveflange (1040, 1060) orthogonal to said elements. 36/ A bag according toclaim 3 or 29, characterized by the fact that at least one of the twoelements (104, 106) provided on the support sheets is provided at itstip with an orthogonal flange (1060) to rest against the inside face ofthe opposite sheet (16). 37/ A bag according to claim 3 or 29,characterized by the fact that at least one of the two elements (104,106) provided on the support films is fitted at its tip with a roundedbulge (1042, 1062). 38/ A bag according to claim 31, characterized bythe fact that the cursor (50) is also provided at the end of said rim(53, 55) with a bead (532) directed towards its web (56) to urge the twojuxtaposed elements (104, 106) to press against each other via theiradjacent flanks (103, 105). 39/ A bag according to any one of claims 1to 38, characterized by the fact that the portions of the support films(16, 18) carrying the closure strips (20, 22) and the leakproofing means(100) are not situated directly in line with the sheets constituting thebody of the bag, but are offset towards the outside of the bag viarespective setbacks (1600, 1800). 40/ A bag according to claim 39,characterized by the fact that one of the offsets (1800) is itselfprovided with an extension (1802) directed towards the opposite supportsheet (16). 41/ A bag according to claim 3 or 29, characterized by thefact that at least one of the two elements (104 or 106) presentsthickness that increases towards its tip or possesses a sloping flank sothat it exerts a force on the juxtaposed other element (106 or 104) whenthe bag is in its closed position. 42/ A bag according to any one ofclaims 1 to 41, characterized by the fact that the leakproofing means(100) comprise structures that are flexible and resilient so as to bedeformable when the bag is closed. 43/ A bag according to any one ofclaims 1 to 42, characterized by the fact that the leakproofing means(100) comprise at least one curved, flexible, and resilient lip (130)secured to the sheet (18) carrying one of the closure strips (22). 44/ Abag according to claim 43, characterized by the fact that the lip (130)is formed by a sector of a cylinder whose angle at the center is greaterthan 180°. 45/ A bag according to claim 43 or 44, characterized by thefact that in the open state of the bag, said lip (130) extends beyondthe associated closure strip (22) so that in the closed state of thebag, said lip (130) exerts pressure on the opposite sheet (16). 46/ Abag according to any one of claims 43 to 45, characterized by the factthat the position of the lip (130) and the shape of said lip (130) aresuch that said lip (130), when resting against the opposite sheet (16)receives reaction which urges it itself to bear against one of theclosure strips. 47/ A bag according to claim 46, characterized by thefact that the urging of the lip (130) to bear against the female closureelement (22) is reinforced by the presence of beads (520, 540) on theinside surfaces of the flanks (52, 54) of the cursor (50). 48/ A bagaccording to claim 47, characterized by the fact that the beads (520,540) converge towards the top web (56) of the cursor (50) on goingtowards the end of the cursor (50) which is situated beside the openingof the bag. 49/ A bag according to any one of claims 1 to 48,characterized by the fact that each of the two sheets (16, 18) isprovided on its inside surface with a resilient lip (130) in the form ofa sector of a cylinder, which lips are designed to bear against eachother via their tips when the bag is closed. 50/ A bag according to anyone of claims 1 to 48, characterized by the fact that each of the twosheets (16, 18) is provided on its inside surface with a resilient lip(130) in the form of a cylindrical sector, the lips being designed to bejuxtaposed laterally. 51/ A bag according to any one of claims 1 to 50,characterized by the fact that, in the vicinity of its mouth (12) itincludes means (150) situated on the side of the closure strips (20, 22)opposite from the side on which said additional leakproofing means (100)are situated, and adapted to define thrust between opposing inside facesof the walls of the bag, and means (520, 540) are provided on the cursor(50) to urge the walls of the bag inwards in a zone of said walls lyingbetween the additional leakproofing means (100) and the thrust means(150). 52/ A bag according to claim 51, characterized by the fact thaturging takes place in register with the closure strips (20, 22). 53/ Abag according to claim 51 or 52, characterized by the fact that theadditional leakproofing means (100) are situated inside the closurestrips (20, 22) while the thrust defining means (150) are situated onthe outside of the closure strips (20, 22). 54/ A bag according to anyone of claims 51 to 53, characterized by the fact that the additionalleakproofing means (100) are formed by two flexible and resilient lips(170, 172). 55/ A bag according to any one of claims 51 to 54,characterized by the fact that the thrust means (150) are formed by twoelements (152, 154) secured respectively to the inside faces of thewalls (16, 18) at the mouth of the bag. 56/ A bag according to claim 55,characterized by the fact that said elements (152, 154) thrust againsteach other in a midplane of the bag when the bag is in its closedposition. 57/ A bag according to claim 55, characterized by the factthat said elements (152, 154) thrust against each other away from themidplane of the bag when the bag is in its closed position. 58/ A bagaccording to any one of claims 51 to 57, characterized by the fact thatthe thrust means (150) are made of the same material(s) as the walls(16, 18) of the bag, preferably by extrusion. 59/ A bag according to anyone of claims 51 to 57, characterized by the fact that the thrust means(150) are made of the same material(s) as the add-on support webs,preferably by extrusion, e.g. by being attached to the walls (16, 18) ofthe bag by heat sealing or adhesive. 60/ A bag according to any one ofclaims 51 to 59, characterized by the fact that the wall segments lyingbetween the leakproofing means (100) and the thrust means (150) arethicker than the sheets (16, 18) constituting the remainder and themajor portion of the bags. 61/ A bag according to any one of claims 51to 60, characterized by the fact that the urging means comprise beads(520, 540) on the inside surfaces of the flanges (52, 54) of the cursor(50). 62/ A bag according to any one of claims 51 to 61, characterizedby the fact that the urging means comprise beads on the walls of thebag. 63/ A bag according to claim 61 or 62, characterized by the factthat the beads (520, 540) are provided in register with the closurestrips (20, 22). 64/ A bag according to any one of claims 51 to 63,characterized by the fact that the facing ends of the elements (152,154) forming the thrust means are enlarged, e.g. having a rightcross-section that is generally triangular. 65/ A bag according to anyone of claims 1 to 64, characterized by the fact that the elementsmaking up the leakproofing means (100) are coextruded with the bagand/or the closure strips out of a material that is more flexible thanthe material forming said bag or strips, e.g. a copolymer of ethylene ora synthetic elastomer. 66/ A bag according to any one of claims 1 to 65,characterized by the fact that said additional means in relief areplaced in register with the flanks of the cursor. 67/ A film for makinga bag according to any one of claims 1 to 66, characterized by the factthat it includes complementary closure strips (20, 22) actuatable by acursor (50) together with additional means in relief (100) disposed onthe insides of the closure strips (20, 22) for the purpose of providingsealing by forming a barrier between the sheets (16, 18) that are toform the bag, when the bag is in its closed position. 68/ A filmaccording to claim 67, characterized by the fact that the additionalmeans in relief providing sealing (100) are constituted by at least onebead (102; 104, 106). 69/ A film according to claim 67 or 68,characterized by the fact that the additional means in relief provingsealing (100) are constituted by two beads (104, 106). 70/ A filmaccording to claim 67, characterized by the fact that the additionalmeans in relief providing sealing (100) are constituted by complementarymale/female elements (110, 112). 71/ A film according to claim 70,characterized by the fact that the male element (110) is of section thatis substantially triangular. 72/ A film according to claim 70 or 71,characterized by the fact that the two lips (1120 and 1122) of thefemale element (112) are asymmetrical. 73/ A film according to claim 67,characterized by the fact that the additional means in relief providingsealing (100) are constituted by elements (104, 106) designed to bejuxtaposed and to bear against one another via their facing adjacentflanks (103, 105) that are generally perpendicular to the sheets (16 and18). 74/ A film according to claim 67, characterized by the fact thatthe additional means in relief providing sealing (100) comprise at leastone curved lip (130) that is flexible and resilient. 75/ A filmaccording to any one of claims 67 to 74, characterized by the fact thatit includes means (150) situated opposite said additional sealing means(100) relative to the closure strips (20, 22) and adapted to cause theopposite inside faces of the bag walls to bear against one another. 76/An extruded tape for making a bag according to any one of claims 1 to66, characterized by the fact that it includes means in relief (100)disposed on the inside of the closure strips (20, 22), and designed toprovide sealing by forming a barrier between the sheets (16, 18)designed to form the bag, when the bag is in its closed position. 77/ Atape according to claim 76, characterized by the fact that it furtherhas at least one closure strip (20, 22) that is actuatable by a cursor(50) on a support web common to said means in relief (100). 78/ A tapeaccording to claim 76 or 77, characterized by the fact that the means inrelief providing sealing (100) are constituted by at least one bead(102; 104, 106). 79/ A tape according to any one of claims 76 to 78,characterized by the fact that the means in relief providing sealing(100) are constituted by two beads (104, 106). 80/ A tape according toclaim 76 or 77, characterized by the fact that the means in reliefproviding sealing (100) are constituted by male/female elements (110,112). 81/ A tape according to claim 80, characterized by the fact thatthe male element (110) is of a section that is substantially triangular.82/ A tape according to claim 80 or 81, characterized by the fact thatthe two lips (1120 and 1122) of the female element (112) areasymmetrical. 83/ A tape according to any one of claims 76 to 82,characterized by the fact that the additional means in relief providingsealing (100) are made up of elements (104, 106) designed to bejuxtaposed and to bear against one another via their facing adjacentflanks (103, 105) that are generally perpendicular to the sheets (16 and18). 84/ A tape according to any one of claims 76 to 83, characterizedby the fact that the additional means in relief providing sealing (100)comprise at least one curved lip (130) that is flexible and resilient.85/ A tape according to any one of claims 76 to 84, characterized by thefact that it includes means (150) situated opposite said additionalsealing means (100) relative to the closure strips (20, 22) and adaptedto cause the opposite inside faces of the walls of the bag to bearagainst each other. 86/ A bag according to any one of claims 1 to 66,comprising two generally parallel sheets (16, 18) forming the main wallsof the bag, complementary closure strips (20, 22) fixed to respectiveones of said sheets (16, 18) in the vicinity of the mouth of the bag,and a cursor (50) having two side flanges (52, 54) interconnected by aweb (56), the flanges being placed on the outsides of the sheets (16,18) at the mouth of the bag and co-operating with a central elongatetongue (59) to define two converging passages (590, 592) for thecomplementary closure strips (20, 22), the bag being characterized bythe facts that the tongue (59) is interrupted so as to be set back fromthe longitudinal end of the cursor (50), at least at the wider end ofthe cursor corresponding to the diverging ends of the passages (590,592), and that the side flanges (52, 54) are provided in the vicinity oftheir free edges remote from the web (56) with urging means (520, 540;100) for urging the sheets (16, 18) of the bag towards each other, saidmeans occupying the entire longitudinal extent of the tongue (59) andextending longitudinally beyond each end thereof so as to ensure thatthe bag is leakproof when it is in its closed position. 87/ A bagaccording to claim 86, characterized by the fact that the urging meansare constituted by ribs (520, 540) projecting inwards from the cursor(50) from the edges of its flanges (52, 54) remote from the web (56) orfrom portions of the height of the inside surfaces of said flanges (52,54) extending between the free edges of the flanges (52, 54) and the web(56). 88/ A bag according to claim 87, characterized by the fact thatthe ribs (520, 540) are situated beyond the tongue (59), and not leveltherewith. 89/ A bag according to claim 87 or 88, characterized by thefact that the ribs (520, 540) extend over the entire length of thecursor (50) while the tongue (59) is interrupted in the vicinity of itsbroader end at a distance (l₁) from the end of the cursor (50). 90/ Abag according to any one of claims 86 to 89, characterized by the factthat the tongue (59) is also interrupted close to its narrower end,adjacent to the converging ends of the passages (590, 592), at adistance (l₂) from the end of the cursor (50). 91/ A bag according toany one of claims 87 to 90, characterized by the fact that the width(l₆) of the empty space defined between the tips of the ribs (520, 540)is substantially equal to the sum of the thicknesses of the sheets (16,18) at the mouth of the bag. 92/ A bag according to any one of claims 87to 91, characterized by the fact that the cursor has two ribs (520, 540)that are symmetrical and of the same height, one on each of its flanges(52, 54). 93/ A bag according to any one of claims 87 to 91,characterized by the fact that the cursor (50) has ribs (520, 540) thatare asymmetrical, or have a single rib on one of her flanges (52, 54) ofthe cursor (50). 94/ A bag according to any one of claims 86 to 93,characterized by the fact that the distance (l₁) between the broad endof the tongue (59) and the end of the cursor lies in the range 1 mm to10 mm, and is preferably about 3 mm. 95/ A bag according to any one ofclaims 86 to 94, characterized by the fact that the distance (l₂)between the narrow end of the tongue (59) and the end of the cursor liesin the range 0.5 mm to 10 mm, and is most preferably about 4 mm. 96/ Abag according to any one of claims 86 to 95, characterized by the factthat the height (l₃) of the tongue (59) lies in the range 2 mm to 7 mm,and is preferably about 3 mm. 97/ A bag according to any one of claims86 to 96, characterized by the fact that the distance (l₄) between thetip of the tongue (59) and the urging means (520, 540) lies in the range5 mm to 15 mm, and is most preferably about 8 mm. 98/ A bag according toany one of claims 86 to 97, characterized by the fact that the width(l₅) of the tongue (59) at its broad end lies in the range 0.3 mm to 2mm, and is preferably about 0.5 mm. 99/ A bag according to any one ofclaims 86 to 98, characterized by the fact that the width (l₆) of theopening provided between the urging means (520, 540) lies in the range50 μm to 2.5 mm, and is most preferably about 200 μm. 100/ A bagaccording to any one of claims 86 to 99, characterized by the fact thatthe ratio (l₁/l₅) of the distance (l₁) between the broad end of thetongue (59) and the end of the cursor over the thickness (l₅) of thetongue (59) at its broad end preferably lies in the range 0.5 to 30, andmost preferably is about
 6. 101/ A bag according to any one of claims 86to 100, characterized by the fact that the ratio (l₂/l₅) of the distance(l₂) between the narrow end of the tongue (59) and the end of the cursorover the thickness (l₅) of the tongue (59) at its broad end preferablylies in the range 2.5 to 30, and most preferably is about
 8. 102/ A bagaccording to any one of claims 86 to 101, characterized by the fact thatthe ratio (l₁/l₃) of the distance (l₁) between the broad end of thetongue (59) and the end of the cursor over the height (l₃) of the tongue(59) preferably lies in the range 0.5 to 5, and most preferably isabout
 1. 103/ A bag according to any one of claims 86 to 102,characterized by the fact that the ratio (l₂/l₃) of the distance (l₂)between the narrow end of the tongue (59) and the end of the cursor overthe height (l₃) of the tongue (59) preferably lies in the range 0.1 to5, and most preferably is about 1.3. 104/ A bag according to any one ofclaims 86 to 103, characterized by the fact that the ratio (l₁/l₄) ofthe distance (l₁) between the broad end of the tongue (59) and the endof the cursor over the thickness (l₄) between the tip of the tongue (59)and the urging means (520, 540) preferably lies in the range 0.05 to 2,and most preferably is about 0.4. 105/ A bag according to any one ofclaims 86 to 104, characterized by the fact that the ratio (l₂/l₄) ofthe distance (l₂) between the narrow end of the tongue (59) and the endof the cursor over the thickness (l₄) between the tip of the tongue (59)and the urging means (520, 540) preferably lies in the range 0.05 to 2,and most preferably is about 0.5.